The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Modern multiple speed motor vehicle automatic transmissions typically include a pressurized oil system including a logic or shift control assembly, a plurality of hydraulically operated clutches and brakes and an oil pump which provides a flow of pressurized oil.
The pressurized oil is supplied to the various assemblies and is also utilized to lubricate and cool bearings and various assemblies such as clutches and brakes whereupon it is returned to a sump from which the pump draws oil, pressurizes it and recirculates it.
During hard vehicle acceleration, the inertia of the oil in the sump of the transmission will cause it to move to and accumulate in the rear of the transmission housing. The oil charge within the transmission is selected to ensure that, notwithstanding this accumulation, the filter inlet in the sump will always be submerged in the oil to prevent oil starvation and allow the pump to draw in air. Should this occur, the pump will cavitate and the delivered oil pressure may drop.
One apparent solution to this problem is simply to increase the oil charge in the transmission. This solution is generally unacceptable, however, for at least two reasons. First of all, an increased oil charge simply adds to the weight of the vehicle. Second of all, due to the significant expansion of the oil as its temperature increases, an increased oil charge sufficient to positively prevent pump starvation during rapid acceleration at cold temperatures will result in an oil volume at high temperatures that will impinge upon rotating members within the transmission. This is undesirable as it can cause power loss, increased frictional heating of the oil and decreased performance of the powertrain.
Another approach has been to secure baffles to the inside of the transmission oil pan to retard oil flow to the rear of the oil pan and transmission during acceleration. While reasonably effective, the baffles increase the weight of the oil pan and add to its complexity and production cost.
From the foregoing explanation, it is apparent that improvements in the art of fluid motion control within gearboxes and transmissions would be desirable and the present invention is so directed.